After a guy has an orgasm and he shoots out so much semen, it's almost as if there's no more left in his tank and he needs to restock. The reason for cumming so much is probably due to the fact that the guy was saving his load and got a real good hand/blow job.

After I had saved my cum for 2 weeks by not masturbating, I went over to her house, and I wasn't expecting what she was about to do. She went into my pants, pulled out my dick and started squeezing it and tugging it so hard, and it felt soooooo good since I haven't wanked it in so long, then when I cummed, I had so much stocked up, it completely covered her hand and I was left drained.